The present invention relates to a seamless steel pipe manufacturing installation and more particularly to a seamless steel pipe manufacturing installation comprising a highly efficient line arrangement in which a rolling line and a finishing line are matched in capacity with each other and are operated as a continuous process line.
It is well known in the art that in the manufacture of seamless steel pipes by hot rolling, the pipes produced by the rolling line including piercing, rolling and sizing mills are divided into as-rolled pipes requiring no heat treatment and those to be heat-treated which require a special heat treatment. More specifically, the as-rolled pipes are transferred from the rolling line to a cooling equipment such as a cooling bed and the pipes to be heat-treated are transferred to a heat treating line including a heating furnace, quenching unit, reheating furnace, etc.
With the above-described line arrangement, not only a kick-out mechanism is required for each line but also a vast installation space is naturally required and the equipment layout also becomes complicated. For instance, in the manufacture of oil well pipes requiring mass handling, if the pipes to be heat-treated must be subjected to such a conditioning processing such as threading of the pipe ends after the heat treatment as in the case of the as-rolled pipes, it is necessary to transfer either the pipes to be heat-treated or the as-rolled pipes to a finishing equipment for thread cutting or the like if the line arrangement is such that the as-rolled pipes and the pipes to be heat-treated are transferred to the following processing equipment by way of separate lines as in the previously mentioned case. Even if the pipes are transferred to the finishing equipment, if the finishing equipment is in operation, the efficiency will be deteriorated by a delay due to the waiting time and the number of lines of the finishing equipment must be increased to increase the efficiency, thus making the entire arrangement extremely irrational and uneconomical.
On the other hand, while a great contribution will be made toward improving the efficiency if the equipment including from the rolling line to the finishing lines are combined as a series of consecutive units to form a continuous manufacturing installation, this involves a serious problem of relative balance of capacity between the rolling line and the finishing line. In other words, while various kinds of rolling processes such as the plug mill process, mandrel mill process, etc., are used in the manufacture of hot-finished seamless steel pipes by rolling process, with any of these processes there is an appreciable unbalance of capacity between the capacity of the rolling line and that of the following finishing line for pipe end processing or the like, that is, the capacity of the latter is inferior to that of the former so that even if the rolling line and the finishing line are connected as a single continuous process line, the rolled steel pipes must be temporarily piled for example at the terminal end of the rolling line which is before the finishing line and this gives rise to such problems as deterioration in the efficiency of the line on the whole and the requirement for a space occupied exclusively by the line. Moreover, it has been the practice so that where different finishing operations are required for different types of pipes to be produced, a multiple-exit line construction is employed to provide separate line exits for different kinds of pipes thus giving rise to such disadvantages as making the transfer patch construction of the finishing line complicated and requiring extra transfer time. Further, it has been undeniable that the finishing line comprises a hybrid arrangement of axial and transverse steel pipe transfer lines and thus there are very much wasteful transfer such as wasteful transfer of steel pipes and changes in the direction of transfer of pipes.